Winter 2021 eNewsletter

CIGLR Great Lakes Summer Fellows, Past and Present, Collaborate to Observe Lake Michigan Using an Autonomous Underwater Glider

Great Lakes gliders help monitor water quality and inform hydrodynamic models. Photo Credit: Russ Miller.

Autonomous underwater gliders provide information on key weather, water, hydrodynamic, and biological variables throughout all of the Great Lakes. Gliders are able to traverse programmed routes from one side of a Great Lake to another and collect data from the surface to the deepest depths. They provide researchers with greater horizontal coverage than ships and buoys, and better vertical coverage below the depths observable by satellites.

CIGLR Assistant Research Scientist Michael Fraker, PhD, specializes in Great Lakes ecosystem dynamics research. He is working with mechanical engineers Russ Miller (CIGLR) and Lauren Marshall (NOAA Affiliate, 2019 Great Lakes Summer Fellow), and CIGLR Great Lakes Summer Fellows Anisha Shrestha (2020, Grand Valley State University) and Jake Fredrickson (2021, University of Minnesota – Duluth) to analyze and process an extensive limnological dataset collected by a Slocum glider in southern Lake Michigan. “The Slocum glider moves slowly across the lake in an up-and-down trajectory and is equipped with several sensors to measure water conditions, including temperature, light, and chlorophyll,” said Fraker. “Its deployments last several weeks at a time, and it makes several passes back and forth across the lake, often from near Muskegon, Michigan to Milwaukee, Wisconsin.

“Shrestha and Fredrickson are focused on analyzing the Slocum glider observations, which will help describe variation in the spatial and temporal scales of key limnological variables,” Fraker continued. “The goal of this research is to understand how patchy the lake environment is, and how it changes seasonally and spatially within the lake. This glider data analysis will help us understand how representative a sample is from each location and how far away you can move from a sampling site before the conditions are likely to be different.”

The Lake Michigan ecosystem has undergone substantial change in recent decades due to a variety of factors, including nutrient management and the introduction of invasive dreissenid mussels. As a result, nutrient concentrations and water clarity, among other water quality characteristics, are different. “In response, the Lake Michigan food web, from the phytoplankton and zooplankton all the way up to the fish, has changed,” said Fraker. “Information from the glider observations will help support Lake Michigan food web research by describing some of the physical and lower food web characteristics that influence the distribution and interactions of species. These observations also provide a foundation for management and conservation efforts aimed at maintaining critical ecosystem services.” In combination, this work will help Great Lakes researchers understand more about how the Lake Michigan food web functions and provide the foundation for management and conservation efforts aimed at maintaining critical ecosystem services, such as the vital Lake Michigan fishery.